BEIRUT -- Lebanese special police forces tightened security around the government palace and other official buildings Thursday amid growing fears that the country's political crisis could descend into street battles.
Tensions are mounting over a U.N.-backed tribunal investigating the 2005 assassination of former Prime Minsiter Rafik Hariri. Many fear that the Shiite militant group Hezbollah -- widely expected to be named in the indictments -- will react violently if accused.
A senior security official confirmed to The Associated Press that the security measures in and around Beirut stem from "concerns of movements on the ground by some parties." The official spoke on condition of anonymity in line with regulations.
Special police forces were seen hauling cement barriers around the government house in Beirut and putting up reinforcements around government buildings and banks. Armored personnel carriers deployed in many areas of the city.
The new measures follow the departure from Beirut of Qatari and Turkish mediators after two days of talks that apparently failed to resolve the differences between Lebanon's main rival factions and bring them back together in a coalition government.
The crisis stems from the investigation into the killing of Rafik Hariri and 22 other people in a massive truck bombing along Beirut's waterfront.
The U.N. court filed a sealed draft indictment Monday, touching off a process many fear could ignite new bloodshed nearly six years after the assassination.
Hezbollah denies any role in Hariri's killing and forced the collapse of the government last week when Prime Minister Saad Hariri -- the son of the slain leader -- refused to renounce the tribunal and pull Lebanon's funding for the court.
The militant group says the tribunal is a conspiracy by Israel and the United States. There are concerns that supporters of the group may take to the streets, setting the stage for sectarian fighting similar to Shiite-Sunni street clashes that killed 81 people in 2008.
Hariri was Lebanon's most prominent Sunni leader.
Saad Hariri, who has stayed on as a caretaker prime minister, is scheduled to hold a news conference Thursday evening, his office said.
The collapse of the Western-backed government was a blow to the United States and its Arab allies, including Saudi Arabia and Egypt.
Syria and Saudi Arabia -- who back rival camps in Lebanon -- had for months been trying to find a settlement to the crisis. When those efforts failed, ministers of Hezbollah and their allies pulled out of the unity Cabinet, toppling the government.
On Wednesday, Saudi Arabia said it was abandoning efforts to mediate, dealing a setback to American diplomacy in the region and raising concerns in Lebanon the crisis was headed for a confrontation.
Qatar and Turkey tried to pick up on the Saudi and Syrian initiative. But two days of meetings by their foreign ministers with rival Lebanese politicians appeared to have failed to produce a deal.
A statement issued by the two before they left Beirut Thursday said they would consult with their leadership.
The statement, published in the state-run National News Agency, said they had formulated in Beirut a paper that takes into consideration "the political and legal requirements to solve the current crisis in Lebanon."
"But because of some reservations, they decided to stop their efforts in Lebanon at this time and leave Beirut to consult with their leadership," the statement added.
Later in the day Turkish Foreign Minister Ahmet Davutoglu said Turkey and Qatar have passed on a draft to the sides with the hope that "the work could help overcome the problem." He added that after receiving responses from the parties concerned and "realizing that there are hesitations regarding the process itself, we came back for consultations."
The U.N.'s special coordinator for Lebanon, Michael Williams, called for dialogue after a meeting with Christian leader Michel Aoun, a strong Hezbollah ally.
"I conveyed to Gen. Aoun my belief that the current crisis should be resolved in a peaceful and lawful manner," he said.
In a sign of the escalating crisis, Aoun said the opposition would not accept that Hariri, who is staying on as a caretaker prime minister, return to the premiership.